1. Field of the Invention
The present invention relates to a data transfer control device and electronic equipment comprising the same, and, in particular, to a data transfer control device that enables data transfer in accordance with the IEEE 1394 standard between a plurality of nodes connected to a bus, and electronic equipment comprising the same.
2. Description of Related Art
An interface standard called IEEE 1394 has recently been attracting much attention. This IEEE 1394 has standardized high-speed serial bus interfaces that can handle the next generation of multimedia devices. IEEE 1394 makes it possible to handle data that is required to have real-time capabilities, such as moving images. A bus in accordance with IEEE 1394 can be connected not only to peripheral equipment for computers, such as printers, scanners, CD-RW drives, and hard disk drives, but also to domestic appliances such as video cameras, VTRs, and TVs. This standard is therefore expected to enable a dramatic acceleration of the digitalization of electronic equipment.
However, some technical problems have been identified with such a data transfer control device conforming to IEEE 1394, as described below.
That is to say, the current IEEE 1394 standard does make it possible to implement transfer speeds up to a maximum of 400 Mbps. In practice, however, the presence of overhead processing forces the actual transfer speeds of the entire system to be much slower. In other words, the firmware (processing means) running on a CPU require large amounts of time for processes such as preparing for transmitting data, dividing transfer data into packets, and issuing the transfer start command, which means it is not possible to implement high-speed data transfer overall, no matter how fast the data can be transferred over the buses.
A particular problem lies in the fact that a CPU incorporated into peripheral equipment has a lower processing capability than the CPU incorporated into the host system, such as a personal computer. This makes the problem of overhead processing in the firmware and application software extremely serious. It is therefore desirable to provide techniques that are capable of efficiently solving this overhead problem.
In addition, when data is transferred between an initiator (host) such as a personal computer and a target (device) such as a CD-RW drive or printer, there are restrictions that prohibit data transfers that exceed page boundaries within a data buffer (storage means) on the initiator side. If the initiator has specified addresses by an indirect addressing method using a page table, it is not particularly necessary for the target side to consider such restrictions. If the initiator has specified addresses by a direct addressing method, however, a problem is raised in that the target side has to perform data transfers while observing such restrictions.